2008 National Seismic Hazard Maps

2008 National Seismic Hazard Maps-Fault parameters

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Fault Name	State
Madison fault	Montana

GEOMETRY
Dip (degrees)	60/40/50
Dip direction	W
Sense of slip	normal
Rupture top (km)	0
Rupture bottom (km)	15
Rake (degrees)	-90
Length (km)	111

MODEL VALUES
Probability of activity	1
Minimum magnitude	6.5
Maximum magnitude	7.45
b-value	0.8

Assigned Dip	Fault-Parallel Slip Rate	Width	Annual Rate	a-value	Branch Weight
40	0.62	23.3	2.87e-04	1.807	0.2
50	0.52	19.6	2.02e-04	1.654	0.6
60	0.46	17.3	1.58e-04	1.548	0.2

Comments
The assigned preferred vertical slip rate is based on reconnaissance studies by Lundstrom (1986) and Mathieson (1983); both report a slip rate of 0.4 mm/yr for the late Pleistocene. More recent studies by Ruleman (2002) suggest a range of similar slip rates that average 0.4 mm/yr. Dip of fault changed to 50? based on redefined regional default value (Lund, 2006).

Selected References
Mathieson, E.L., 1983, Late Quaternary activity of the Madison Range fault along its 1959 rupture trace, Madison County, Montana: Stanford, California, Stanford University, unpublished M.S. thesis, 169 p., 4 pls. Lundstrom, S.C., 1986, Soil stratigraphy and scarp morphology studies applied to the Quaternary geology of the southern Madison Valley, Montana: Arcata, California, Humboldt State University, unpublished M.S. thesis, 53 p., 1 pl., scale 1:24,000. Ruleman, C.A., III, 2002, Quaternary tectonic activity within the northern arm of the Yellowstone tectonic parabola and associated seismic hazards, southwest Montana: Bozeman, Montana State University, unpublished M.S. thesis, 158 p. Lund, W.R., ed., 2006, Basin and Range Province Earthquake Working Group seismic-hazard recommendations to the U.S. Geological Survey National Seismic Hazard Mapping Program: Utah Geological Survey Open-File Report 477, 23 p, ugspub.nr.utah.gov/publications/open_file_reports/OFR-477.pdf.

Selected References

Mathieson, E.L., 1983, Late Quaternary activity of the Madison Range fault along its 1959 rupture trace, Madison County, Montana: Stanford, California, Stanford University, unpublished M.S. thesis, 169 p., 4 pls.
Lundstrom, S.C., 1986, Soil stratigraphy and scarp morphology studies applied to the Quaternary geology of the southern Madison Valley, Montana: Arcata, California, Humboldt State University, unpublished M.S. thesis, 53 p., 1 pl., scale 1:24,000.
Ruleman, C.A., III, 2002, Quaternary tectonic activity within the northern arm of the Yellowstone tectonic parabola and associated seismic hazards, southwest Montana: Bozeman, Montana State University, unpublished M.S. thesis, 158 p.
Lund, W.R., ed., 2006, Basin and Range Province Earthquake Working Group seismic-hazard recommendations to the U.S. Geological Survey National Seismic Hazard Mapping Program: Utah Geological Survey Open-File Report 477, 23 p, ugspub.nr.utah.gov/publications/open_file_reports/OFR-477.pdf.